Photocatalytic batch reactor operable for converting gaseous, liquid, and supercritical carbon dioxide

ABSTRACT

A photocatalytic batch reactor can include a reactor vessel configured to receive a photocatalyst, the housing having an inlet, an outlet, and an opening configured to allow light to pass into the interior volume. The photocatalytic batch reactor can include a carbon-dioxide pump that is configured to pressurize carbon-dioxide en route to the reactor vessel. The photocatalytic batch reactor is operable in a gas state in which gas carbon-dioxide is supplied to the reactor vessel from a gas carbon-dioxide container. The photocatalytic batch reactor is also operable in a liquid state in which liquid carbon-dioxide is supplied to the reactor vessel from a liquid carbon-dioxide container. The photocatalytic batch reactor is also operable in a supercritical state, in which supercritical carbon-dioxide is supplied via the carbon-dioxide pump.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/345,862 filed May 25, 2022, the entire contents of which are herebyincorporated for all purposes in their entirety.

BACKGROUND OF THE INVENTION

A photocatalytic reactor can convert reactants into products byintroducing light and a catalyst to induce a photocatalysis process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a photocatalytic batch reactor operable forconverting gaseous, liquid, and supercritical carbon-dioxide accordingto certain aspects of the present disclosure.

FIG. 2 is an illustration of an exemplary laboratory setup including aphotocatalytic batch reactor operable for converting gaseous, liquid,and supercritical carbon-dioxide according to certain aspects of thepresent disclosure.

FIGS. 3A and 3B show a schematic of a dopant molecule usable with aphotocatalytic batch reactor operable for converting gaseous, liquid,and supercritical carbon-dioxide according to certain aspects of thepresent disclosure, and a graph of energy data associated therewith.

FIGS. 4A, 4B, and 4C show graphs related to characteristics of differentcatalyst samples, according to certain aspects of the presentdisclosure.

FIG. 5 is a schematic of an alternate configuration for a photocatalyticbatch reactor according to certain aspects of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects and features of the present disclosure relate to areactor that can enable carbon-dioxide conversion reactions to takeplace under a wide range of parameters and conditions. In some examples,the reactor can be a versatile photocatalytic batch reactor. In someexamples, the reactor can operate with carbon-dioxide in a gas state, aliquid state, a supercritical state, or any combination thereof. Thereactor can be capable of operating at temperatures of at least 250° C.and pressures of at least 80 bar. The reactor can operate under any formof light irradiation type and source, such as UV irradiation, visiblelight irradiation, solar irradiation, or any combination thereof. Insome examples, a high-pressure pump can introduce a reducing agent tothe carbon-dioxide, where the reducing agent can be in a gas state, aliquid state, a supercritical state, or any combination thereof. Thereactor can collect gaseous reaction products as well as liquid-solublereaction products. The reactor can be configured to receive aphotocatalyst. The photocatalyst may be introduced in powder form or ina thin film that can be supported on a substrate. In some examples, thereactor can carry out any other type of photocatalytic reactions for airpurification, water remediation, or any other suitable application. Thereactor can also be operable to perform non-catalytic photo-inducedreactions and catalytic non-photo-induced reactions.

FIG. 1 is a schematic of an example of a photocatalytic batch reactor100 operable for converting gaseous, liquid, and supercriticalcarbon-dioxide. In some examples, the photocatalytic batch reactor caninclude a reactor vessel 101 that can contain reactants.

The reactor vessel 101 can include a housing 130 having an interiorvolume. In some examples, the housing 130 can be cylindrical. Thereactor vessel 101 can be cylindrical and made of a metal, such asstainless steel or aluminum. In some examples, the reactor vessel 101can be made of a combination of metals. In some examples, the volume ofthe reactor vessel 101 can be roughly 110 mL.

Additionally, the reactor vessel 101 can include a top lid 138 The toplid 138 can be opened or closed by tightening or loosening screws orother fasteners that may fasten the top lid 138 to the reactor vessel101, for example.

A light source 139 can be positioned proximate to one or more of thecircular sides of the reactor vessel 101 or placed on top of, above, orover the reactor vessel 101. Light emitted from the light source 139 canbe transmitted through a window and into the reactor vessel 101. In someexamples, the window may be positioned in the top lid 138. For example,the top lid 138 may include an open center that can be sized to receivea suitable light permeable material, such as sapphire glass or any othersuitable material. The cylindrical sapphire glass can be held in placeon top of the reactor vessel 101 using rubber O-rings, for example. Thelight emitted from the light source 139 can enable a photocatalyticreaction between a photocatalyst and carbon-dioxide present in thereactor vessel 101.

In some examples, the contents of the reactor can be stirred using amagnetic stirrer 136. For example, the magnetic stirrer 136 can exert amagnetic force on a magnet 134 within the reactor vessel 101. The magnet134 can be moved based on the magnetic force and can stir the contentsof the reactor vessel 101 as a result.

The reactor vessel 101 can include openings for receiving and/orexpelling substances. For example, the reactor vessel 101 can include aninlet 107 for receiving reactants, and an outlet 105 for expellingreaction products. The inlet 107 can include an inlet valve 137 forcontrolling fluid flow with respect to the inlet 107. In some examples,the inlet valve 137 can be a needle valve, or any other suitable valve.

The reactor 100 can include a gas carbon-dioxide container 102 that isconfigured to contain carbon-dioxide in a gaseous state. In someexamples, the pressure of the gas carbon-dioxide container 102 can beregulated up to 10 bars and/or may be capable of operating with at least10 bars.

The reactor 100 can also include a liquid carbon-dioxide container 106that is configured to contain carbon-dioxide in a liquid state. Theliquid carbon-dioxide container 106 can include a tube that can withdrawliquid carbon-dioxide from the liquid carbon-dioxide container 106. Theliquid carbon-dioxide container 106 pressure can be the equilibriumpressure at room temperature, which can be around 62 bar.

The reactor 100 can include a carbon-dioxide pump 108. Thecarbon-dioxide pump 108 can be coupled with the reactor vessel 101, thegas carbon-dioxide container 102, the liquid carbon-dioxide container106, and an air compressor 110. The air compressor 110 can include apressure regulator 103 for regulating air pressure from the aircompressor 110. Liquid carbon-dioxide can be compressed by thecarbon-dioxide pump 108 to generate carbon-dioxide in the supercriticalphase. The carbon-dioxide pump 108 can operate with the help of the aircompressor 110.

The reactor 100 can include a high-pressure pump 112 that can be used asa controlled injection system for fluids at high pressure. Thehigh-pressure pump 112 can flow streams of high-pressure liquids orsupercritical fluids, such as fluids that can be miscible with water ororganic solvents. The high pressure pump 112 can be a specialized pumpwith a fine control system to regulate the flow rate.

The reactor 100 can include a heating jacket 132 that can couple with atemperature controller and temperature sensor. The reactor 100 can usethe temperature controller and the heating jacket 132 to control andmaintain the temperature of the photocatalytic reaction taking placewithin the reactor vessel 101. In some examples, the temperaturecontroller and the heating jacket 132 can be used to control atemperature associated with the reactor 100. For example, the heatingjacket 132 can be used to maintain a suitable range of temperatures forprocessing a particular phase of carbon-dioxide that may be present inthe reactor vessel 101. In an illustrative example, the reactor vessel101 can process a supercritical phase of carbon-dioxide, and the heatingjacket 132 can apply heat to the reactor vessel to maintain atemperature suitable to maintain the supercritical phase ofcarbon-dioxide.

In use, after the addition of photocatalyst, the reactor 100 can besealed by tightening the reactor's top lid. 138. The reactor 100 can bepurged with a feed. In some examples, the feed can be introduced via apurge line 114. The feed can include pure carbon-dioxide or a mixture ofcarbon-dioxide and a reducing agent. The feed can be used to remove airand any other impurities that may be present inside the reactor vessel101. After purging, the flow can be stopped when the batch reactor 100is sufficiently saturated with the feed. In cases where the reaction isnot run in the gas phase, the magnetic stirrer 136 can be used. Afterloading the photocatalyst and purging/saturating the reactor 100 withthe feed, a reactivity test can be initiated by turning on the lightsource 139.

The reactor vessel 101 can be coupled with an outlet valve 140. Theoutlet valve 140 can enable and disable the flow of reaction productsfrom the outlet 105 of the reactor vessel 101. The outlet valve 140 canbe opened to enable product sampling. For example, the outlet valve 140can be opened to enable reaction products contained within the reactionvessel 101 to flow from the reaction vessel 101 and into one or moresamplers for sampling. When sampling, the pressure in the reactor vessel101 can drop slightly. The magnetic stirrer 136 can uniformly mix thephotocatalyst with liquid or supercritical carbon-dioxide.

The reactor 100 can include a gas-phase sampler 148 for collectinggas-phase products. For example, the gas-phase sampler 148 can include aseptum and a gas-tight syringe. A portion of the gas-phase sampler 148can be filled with glass beads to reduce the sampling volume.

The reactor 100 can also include a liquid-phase sampler 154, in whichwater-soluble products may be collected and later transferred to HPLCvials. The liquid-phase sampler 154 can contain de-ionized (DI) water,which may serve as a solvent for the collection of products in theliquid phase. The DI water can trap the gaseous products in the gassampler. The DI water in the liquid-phase sampler 154 can be replacedafter each sampling point.

The reactor 100 can include an outlet valve 140 that can regulate theoutlet flow rate from the outlet 105. The outlet valve 140 can be heatedto prevent products from condensing. In some examples, the outlet valve140 can be a needle valve, or any other suitable valve. In someexamples, the reactor 100 can include a vent line 142. Additionally, thereactor 100 can include a heated needle valve 144 that can be positioneddownstream with respect to the outlet valve 140. The heated needle valve144 can prevent reaction products from condensing while passing throughthe heated needle valve 144.

During sampling, the flow rate can be set by a mass flow controller 146while the outlet valve 140 is opened or closed. This can ensure that thesame amount of product is collected at every sampling point. The massflow controller 146 can be coupled to an ON/OFF valve 150 that canenable or prevent fluids from flowing from the mass flow controller 146.The outlet stream can pass from the outlet valve 140 and into agas-phase sampler 148 and then into the liquid-phase sampler 154.Gas-phase products can be analysed using gas a chromatograph (GC) whileliquid-phase products in a high-performance liquid chromatograph (HPLC).For example, the gas-phase sampler 148 can be coupled to the GC and theliquid-phase sampler 154 can be coupled with the HPLC. To ensure thatthe products are forming from the reduction of carbon-dioxide, a controltest can be performed. In the test, argon gas can used instead ofcarbon-dioxide and the photoreactivity test can be run. In someexamples, a C13 analysis can also be performed.

The reactor 100 can include a flowmeter 160 with a vent 161. Theflowmeter 160 can measure the flow rate at the outlet 105 of the reactor100.

In some examples, the reactor 101 can be operable in a gas state inwhich gaseous carbon-dioxide is supplied to the reactor vessel 101 fromthe gas carbon-dioxide container 102. Additionally, the reactor 101 canbe operable in a liquid state in which liquid carbon-dioxide is suppliedto the reactor vessel 101 from the liquid carbon-dioxide container 106.Additionally, the reactor 101 can be operable in a supercritical state,in which supercritical carbon-dioxide is supplied via the carbon-dioxidepump 108.

FIG. 2 is an illustration of an exemplary laboratory setup including aphotocatalytic batch reactor operable for converting gaseous, liquid,and supercritical carbon-dioxide according to certain aspects of thepresent disclosure. FIG. 2 shows a reactor vessel 204 with a heatingjacket 211 thereon. The reactor vessel 204 is shown atop a magneticstirrer 205 that is configured to magnetically stir the contents of thereactor vessel 204. The reactor vessel 204 is shown beneath anultraviolet lamp 203. The ultraviolet lamp 203 is configured to shinelight into the reactor vessel 204 via a sapphire window 210 atop thereactor vessel 204. The reactor vessel 204 is shown coupled to an outletvalve 206 and an inlet valve 207. The outlet valve 206 is shown coupledto a pair of gas sampling tubes 208 that can be used to sample gasreceived from the outlet valve 206. The gas sampling tubes 208 are showncoupled to a volumetric flow meter 209 that can be used to determine aflow rate of fluids passing through the volumetric flow meter 209. Thereactor vessel 204 is shown coupled to a temperature sensor 202 that canbe used to sense a temperature associated with the reactor vessel 204.The temperature sensor 202 can be used in conjunction with a temperaturecontroller 201. The temperature controller 201 can adjust thetemperature of the reactor vessel 204 via the heating jacket 211. Insome examples, the temperature controller 201 can adjust the temperatureof the reactor vessel 204 based on temperature data received from thetemperature sensor 202.

The photocatalytic reduction of liquid or supercritical carbon-dioxidecan lead to enhancement in product yields. In this work, thephotocatalytic conversion of liquid carbon-dioxide at room temperatureconditions can be investigated under UV light irradiation. A suitablephotocatalyst, namely a copper-doped brookite-rutile TiO2 photocatalystthat can be photo-deposited with platinum nanoparticles and impregnatedwith reduced graphene oxide (rGO-(Pt/Cu—TiO2)), can be used in thereactor, as shown in FIG. 3A. The experimental work can be complementedwith DFT calculations on model brookite and rutile TiO2 surfaces withatomic Cu located on the surface or in the lattice of TiO2. Cu dopingcan alter the electronic properties and performance of thephotocatalyst. Subsequently, the role of Cu in carbon-dioxide adsorptioncan be systematically studied by performing comparative studies onreaction pathways for the reduction of carbon-dioxide into CO.

The copper-doped (1 wt. %) brookite-rutile TiO2 (Cu—TiO2) can beprepared by following a simple sol-gel procedure. Next, platinum (0.5wt. %) can be photo-deposited on Cu—TiO2. Then, reduced graphene oxide(0.5 wt. %) can be impregnated on Pt/Cu—TiO2. The material can becharacterized by XRD, Raman, UV-vis DRS, PL, FT-IR, TEM, STEM-EDS, TPD,among others. A custom-built batch reactor 100 used to test thephotocatalytic activity of the different catalysts in reducingcarbon-dioxide can be designed in-house and can be shown in FIG. 1 . Thecalculations can be carried out using the plane-wave-based DFT method asimplemented in the Vienna ab Initio Simulation Package (VASP). In thepresence of liquid phase, the solvation effect can be considered duringthe energy and geometry optimization based on the periodic continuumsolvation model as implemented in the VASPsol code.

FIG. 3A shows a schematic of a dopant molecule usable with aphotocatalytic batch reactor operable for converting gaseous, liquid,and supercritical carbon-dioxide according to certain aspects of thepresent disclosure, and FIG. 3B shows a graph of energy data associatedtherewith. The photocatalyst molecule is shown having copper andtitanium dioxide.

FIGS. 4A, 4B. and 4C show graphs related to characteristics of differentcatalyst samples, according to certain aspects of the presentdisclosure. In particular, FIG. 4A depicts photoluminescence spectraassociated with photocatalyst dopant molecules. The photoluminescencespectra can be used to determine photocatalytic activity ofphotocatalysts during a reaction taking place in the reactor. FIG. 4Bdepicts UV-vis diffuse reflectance spectra associated with thephotocatalyst dopant molecules. FIG. 4C depicts carbon-dioxidetemperature-programmed desorption peaks of different photocatalystmolecules.

FIG. 5 is a schematic of an alternate configuration for a photocatalyticbatch reactor operable for converting gaseous, liquid, and supercriticalcarbon-dioxide according to certain aspects of the present disclosure.The reactor 500 includes a carbon-dioxide container 501 that can containgaseous carbon-dioxide, liquid carbon-dioxide, or a combination thereof.The carbon-dioxide container 501 includes a pressure regulator valvethat is configured to regulate the pressure of carbon-dioxide flowingtherefrom. The carbon-dioxide container 501 is shown coupled to thereactor vessel 510 via an inlet needle valve 519. The reactor caninclude a sapphire window 512 that can transmit light from a lightsource 510 into an interior of the reactor vessel 510. The reactor 500can include a magnetic stirrer 517 that can be configured to stir thecontents of the reactor vessel 510 via a magnet 518 that is positionedwithin the reactor vessel 510. The reactor 500 includes an outlet 503for expelling reaction products from the reactor vessel 510. The outlet503 can be coupled to an outlet valve 516 that can enable or disable theflow of reaction products from the reactor vessel 510. The reactor 500can include a needle valve 520 for retrieving reaction products from thereactor vessel 510 and transmitting the reaction products elsewhere. Theneedle valve 520 can be coupled to an ON/OFF valve 516 that can enableor disable the flow of reaction products past the ON/OFF valve 516. Agas sampler 548 and/or a liquid sampler 554 can be included in the flowpath from the outlet 503. A flow meter 560 can also be included, such asfor measuring an amount of fluid flow therethrough.

In the preceding description, various embodiments have been described.For purposes of explanation, specific configurations and details havebeen set forth in order to provide a thorough understanding of theembodiments. However, it will also be apparent to one skilled in the artthat the embodiments may be practiced without the specific details.Furthermore, well-known features may have been omitted or simplified inorder not to obscure the embodiment being described.

Some embodiments of the present disclosure include a system includingone or more data processors. In some embodiments, the system includes anon-transitory computer readable storage medium containing instructionswhich, when executed on the one or more data processors, cause the oneor more data processors to perform part or all of one or more methodsand/or part or all of one or more processes and workflows disclosedherein. Some embodiments of the present disclosure include acomputer-program product tangibly embodied in a non-transitorymachine-readable storage medium, including instructions configured tocause one or more data processors to perform part or all of one or moremethods and/or part or all of one or more processes disclosed herein.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

Thus, it should be understood that although the present invention asclaimed has been specifically disclosed by embodiments and optionalfeatures, modification and variation of the concepts herein disclosedmay be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope ofthis invention as defined by the appended claims.

The description provides preferred exemplary embodiments only, and isnot intended to limit the scope, applicability or configuration of thedisclosure. Rather, the ensuing description of the preferred exemplaryembodiments will provide those skilled in the art with an enablingdescription for implementing various embodiments. It is understood thatvarious changes may be made in the function and arrangement of elementswithout departing from the spirit and scope as set forth in the appendedclaims.

Specific details are given in the description to provide a thoroughunderstanding of the embodiments. However, it will be understood thatthe embodiments may be practiced without these specific details. Forexample, specific computational models, systems, networks, processes,and other components may be shown as components in block diagram form inorder not to obscure the embodiments in unnecessary detail. In otherinstances, well-known circuits, processes, algorithms, structures, andtechniques may be shown without unnecessary detail in order to avoidobscuring the embodiments.

What is claimed is:
 1. A photocatalytic batch reactor, comprising: areactor vessel comprising a housing defining an interior volumeconfigured to receive a photocatalyst, the housing having an inlet, anoutlet, and an opening configured to allow light to pass into theinterior volume; a light source positioned to direct the light into theinterior volume through the opening; a carbon-dioxide pump that isconfigured to pressurize carbon-dioxide en route to the reactor vessel;a gas carbon-dioxide container coupled with the inlet of the reactorvessel, the gas carbon-dioxide container configured to flow gascarbon-dioxide to the interior volume of the reactor vessel; a liquidcarbon-dioxide container coupled with the inlet of the reactor vessel,the liquid carbon-dioxide container configured to flow liquidcarbon-dioxide to the interior volume of the reactor vessel; and anoutlet valve coupled with the outlet of the reactor vessel, the outletvalve configured to flow an outlet stream from the interior volume ofthe reactor vessel, wherein the reactor is operable in at least thefollowing three states: a gas state in which gas carbon-dioxide issupplied to the reactor vessel from the gas carbon-dioxide container; aliquid state in which liquid carbon-dioxide is supplied to the reactorvessel from the liquid carbon-dioxide container; and a supercriticalstate, in which supercritical carbon-dioxide is supplied via thecarbon-dioxide pump.
 2. The photocatalytic batch reactor of claim 1,further comprising a magnetic stirrer that is positioned proximate thereactor vessel and is configured to stir the contents of the reactorvessel via a magnet positioned within the reactor vessel.
 3. Thephotocatalytic batch reactor of claim 1, further comprising ahigh-pressure pump that is coupled with the reactor vessel for flowinghigh pressure fluids into the reactor vessel.
 4. The photocatalyticbatch reactor of claim 1, further comprising: a gas-phase sampler thatis configured to receive gas-phase reaction products from the reactorvessel; and a liquid-phase sampler that is configured to receiveliquid-phase reaction products from the reactor vessel.
 5. Thephotocatalytic batch reactor of claim 1, wherein the photocatalyticbatch reactor is operable at least at an operating temperature of 250degrees Celsius and at least at an operating pressure of 80 bar.
 6. Thephotocatalytic batch reactor of claim 1, wherein the outlet valveincludes a heated needle valve that is operable to apply heat toreaction products within the valve for preventing the reaction productsfrom condensing.
 7. The photocatalytic batch reactor of claim 1, whereinthe opening includes a sapphire crystal.
 8. The photocatalytic batchreactor of claim 1, further comprising a heating jacket that is operablevia a temperature controller for applying heat to contents of thereactor vessel.
 9. The photocatalytic batch reactor of claim 1, whereinthe carbon-dioxide pump is coupled with an air compressor that isoperable to provide additional pressure to carbon-dioxide flowingthrough the carbon-dioxide pump.
 10. The photocatalytic batch reactor ofclaim 1, further comprising a flowmeter positioned proximate the outletvalve for measuring and controlling a flow rate of the outlet valve.